Defective Black TiO2 Nanotube Arrays for Enhanced Photocatalytic and Photoelectrochemical Applications

Black TiO2 is of great interest for efficient solar harvest in photocatalytic and photoelectrochemical applications. In this work, we report a convenient, low-cost, and safe method for producing black TiO2 nanotube arrays (TNTAs). By a simple soaking in an ethylene glycol (EG) solution of NH4F, the as-anodic TNTAs turn black, with a substantial amount of oxygen vacancies and Ti3(+ )sites induced. The thus-obtained black TNTAs deliver greatly enhanced photoelectrochemical and photocatalytic performance of high stability.